1. Field of the Invention
The present invention relates to a semiconductor device, and more particularly to a Fin Field Effect Transistor (FinFET) with a strained channel and electrically separate gates that are independently controllable, and to a method of forming the FinFET device.
2. Description of the Related Art
Fin FETs are considered promising candidates for complementary metal oxide semiconductor (CMOS) device scaling (e.g., see Hu Chenming et al., U.S. Pat. No. 6,413,802 entitled “FinFET transistor structures having a double gate channel extending vertically from a substrate and methods of manufacture”).
The fabrication of a FinFET is generally simpler than most other double-gate structures, although the channel thickness control is problematic in most known approaches (e.g., see U.S. Pat. No. 6,413,802; Yang-Kyu Choi et al., “Spacer FinFET: nanoscale double-gate CMOS technology for the terabit era”, Solid-State Electronics, 46, p. 1595, (2002)).
To increase the device current drive, high carrier mobility is required. MOSFETs with high carrier mobility are made by fabricating the device on strained silicon (e.g., see K. Rim et al. “Fabrication and Analysis of Deep Submicron Strained-Si N-MOSFET's”, IEEE Trans. Electron Devices, 47(7), p. 1406, (2000)).
The conventional techniques for making strained silicon are applicable for planar devices such as the conventional MOSFET. Examples for such techniques are a graded buffer SiGe layer (e.g., see P. M. Mooney, Materials Science and Engineering Reports R17, p. 105 (1996) and references cited therein), and the relaxation by ion implantation and anneal (e.g., see U.S. Pat. No. 6,593,625 by S. H. Christiansen et al., entitled “Relaxed SiGe layers on Si or silicon on insulator substrates by ion implantation and thermal annealing”).
Unfortunately, the FinFET is a non-planar device, where the plane of current conduction (i.e., the Fin) is perpendicular to the wafer surface. This makes the FinFET non-compatible with conventional strain silicon fabrication techniques.